A number of power tools have been produced to facilitate forming a work piece into a desired shape. One such power tool is a table saw. A wide range of table saws are available for a variety of uses. Some table saws such as cabinet table saws are very heavy and relatively immobile. Other table saws, sometimes referred to as jobsite table saws, are relatively light. Jobsite table saws are thus portable so that a worker can position the table saw at a job site. Some accuracy is typically sacrificed in making a table saw sufficiently light to be mobile. The convenience of locating a table saw at a job site, however, makes job site table saws very desirable in applications such as general construction projects.
All table saws, including cabinet table saws and job site table saws, present a safety concern because the saw blade of the table saw is typically very sharp and moving at a high rate of speed. Accordingly, severe injury such as severed digits and deep lacerations can occur almost instantaneously. A number of different safety systems have been developed for table saws in response to the dangers inherent in an exposed blade moving at high speed. One such safety system is a blade guard. Blade guards movably enclose the saw blade, thereby providing a physical barrier that must be moved before the rotating blade is exposed. While blade guards are effective to prevent some injuries, the blade guards can be removed by a user either for convenience of using the table saw or because the blade guard is not compatible for use with a particular shaping device. By way of example, a blade guard is typically not compatible with a dado blade and must typically be removed when performing non-through cuts.
Table saw safety systems have also been developed which are intended to stop the blade when a user's hand approaches or touches the blade. Various stopping devices have been developed including braking devices which are physically inserted into the teeth of the blade. Such approaches are extremely effective. Upon actuation of this type of braking device, however, the blade is typically ruined because of the braking member. Additionally, the braking member is typically destroyed. Accordingly, each time the safety device is actuated; significant resources must be expended to replace the blade and the braking member. Another shortcoming of this type of safety device is that the shaping device must be toothed. Moreover, if a spare blade and braking member are not on hand, a user must travel to a store to obtain replacements. Thus, while effective, this type of safety system can be expensive and inconvenient.
Some safety systems incorporating blade braking systems also move the blade below the surface of the table saw once the blade has been stopped. In this type of system, a latch is typically used to maintain the blade in position above the table saw surface until the braking system is activated.
Once a safety system has been activated and the unsafe condition cleared, the table saw may be returned to operation. Because the blade has been moved, the blade must be realigned before further work piece shaping can occur. Realignment of the blade may be more difficult as a result of the force used to move the blade at the speed desired to reduce injuries. The large amount of force may result in some changes in the relative positions of components which, while acceptable for operation of the table saw, provide reduced accuracy in the alignment of the blade with respect to the work support surface.
While table saws are typically provided with components which allow accurate alignment of the blade with respect to the work piece support surface, reference devices needed to function as a guide for the realignment process may not be readily available. Moreover, alignment of the blade can require a substantial delay in returning the table saw to service.
In view of the foregoing, it would be advantageous to provide a power tool with a safety system that did not damage the blade or other shaping device when the safety system is activated. A further advantage would be realized by a safety system that could be repeatedly activated without the need for realignment of the blade or other shaping device with respect to a work piece support surface.